1.5mm smd led

It is a 1.5mm Blue Surface Mount LED. An LED is a two-lead semiconductor light source, which emits lights when activated. When an appropriate voltage is applied to the LED terminal, then the electrons are able to recombine with the electron holes within the device and release energy in the form of photons. This effect is known as electroluminescence. The color of the LED is determined by the energy bandgap of the semiconductor.